In both residential and non-residential electrical installations a system comprising runs of conduit is very often employed for distribution of electrical wiring throughout premises. By "conduit" is meant metal or plastic pipe or tubing for carrying insulated electrical wires. Metal conduit has the added advantage of providing a very positive ground return path. Such conduit provides a convenient and effective way to gather electrical wires or conductors together, to protect the wires against the elements and against mechanical disturbances, and to extend them from an electrical distribution panel, for example, to the various sites of electrical fixtures, machine tools, appliances and outlets as may be desired throughout the premises. In addition to insulated wires designed to carry relatively high voltages and currents, i.e. so called power carrying wire of about 110 up to 480 volts and 10 up to 500 amps, conduit is also widely used to contain optic fibers and/or signal or control wire, i.e. wire operating at voltages of a maximum of 110 volts down to millivolts, such wire serving to actuate switches and thermostats or, in the case of telephone wire, to communicate data. The conduit fittings of the present invention are applicable to conduits for carrying power cable or wire, signal wire and/or optic fiber cable.
The prior art type of conduit fittings which are pertinent to the present invention are known by tradenames including "Electrolets", "Condulets", "Unilets", etc. Such fittings enable sharp changes in direction to be made in the conduit run, and in this regard are to be contrasted with elbows which are pre-bent portions of conduit which may be coupled with straight conduit runs by suitable connectors. Conduit fittings typically include a body, two hollow threaded stubs or shanks extending from the body, usually along loci separated by either 90 or 180 degrees, an interior compartment within the body and communicating with the hollow shanks, and a removable weathertight cover plate. Usually, the cover plate is attached to the body by screws, and it may include gasket means for weathertight sealing. The above described, prior art conduit fittings and also the conduit fittings of the type contemplated by the present invention are for above-ground and below-ground vault installations.
The tubular conduit attach to the fittings at each shank of the conduit body, typically by tapered threads (in the case of thickwall conduit) or via threaded nipples (in the case of thinwall conduit). Access provided to the interior compartment by removal of the cover plate enables the electrician to pull the electrical wires through each run, and/or to make solderless joint connections with connectors which fit within the interior compartment of the fitting.
Conduit fittings are typically formed by casting of malleable iron or aluminum, or molding of suitable plastic material, such as polyvinylchloride, and they typically are threaded with inside tapered female threads, to mate with male tapered threads cut on the end of the conduit or nipple. Tapered threads cause the conduit or nipple and the fitting to become securely engaged. If plastic conduit is to be utilized, the conduit body can likewise be plastic and the shanks need not be threaded, but rather may have an inside diameter approximately equivalent to the outside diameter of the conduit to facilitate mating via solvent bonding or other adhesive techniques.
One principal drawback of the prior art conduit fittings is that they, of necessity, come in a wide variety of sizes and shapes. Basically, the electrician or other user has to have available a wide variety of different conduit fittings for a particular job. Standard conduit fittings are coded E, LB, LL, LR, TA, etc. The E fitting is provided as an end fitting for terminating a conduit run at the situs of a machine having an insulated cable running from its motor. The E fitting usually includes a cover having a grommet or cable clamp therein for mechanically securing the insulated cable and for passing its conductors to the interior compartment. The LB fitting provides a right angle turn along a locus extending oppositely away from the removable cover. The LL fitting provides a right angle turn along a locus extending to the left of the removable cover. The LR fitting provides a right angle turn along a locus extending to the right of the removable cover. The TA fitting provides two shanks at opposite longitudinal ends of the body, and a "tee" shank extending on one or more sides of the body, and so forth. Not only must the craftsman carry a sufficient supply of all of these fittings to the job site, there must be a variety of fittings for each size of conduit likely to be employed on the job. Thus, for a craftsman to be adequately equipped, a very large variety of conduit fittings must be available.
One further drawback of existing conduit fitting designs is that such designs do not provide for any direct mechanical attachment to a supporting substrate such as a wall, ceiling or vertical post. Rather, the conduit attaching to the prior fitting is typically supported by clamps, straps, etc. Despite the fact that the conduit fittings of the prior art are not directly attachable to a support substrate, often they have been used to supporlight fixtures and other appliances which present mechanical loads and stresses to the fittings. Since the fittings are typically formed as castings, they are not readily adaptable to direct attachment to the support substrate, and attempts at drilling holes through the base to permit utilization of attachment means such as a screw have left the fitting weakened and also subject to unwanted moisture intrusions.
A particular drawback of prior art conduit fittings is that once they have been installed, subsequent changes in arrangement of the connected conduit, such as attachment of additional branch conduit runs, has typically required that the conduit fitting be replaced entirely. This procedure necessitates removal of all existing wires, removal of the conduit fitting, replacement with a new appropriately configured conduit fitting, reinstallation of the original wires and installation of the new wires in the additional run. This procedure has been inconvenient time consuming and expensive.
Thus, a hitherto unsolved need exists for an improved conduit fitting which overcomes the limitations and drawbacks of the prior art designs.